Double action thermostat



s. VERNET 3,407,663

DOUBLE ACTION THERMOSTAT Oct. 29, 1968 2 Sheets-Sheet 2 Filed June 14, 1963 INVENTOR. 158/9/06 l 6/fl6/ %4- LaV/% TTORNEYS United States Patent 3,407,663 DOUBLE ACTION THERMOSTAT Sergius Vernet, Yellow Springs, Ohio, assignor to Antioch College, Yellow Springs, Ohio, a corporation of Ohio Filed June 14, 1963, Ser. No. 287,837 9 Claims. (Cl. 73-3683) This invention relates to thermal responsive elements or temperature responsive force transmitting devices and is more particularly directed to a device of this character having means for providing a plural action power member.

Thermal responsive elements are now widely used as a means for energizing a wide variety of components as a function of changes in ambient temperature. Generally, they comprise a casing having a thermal expansion material contained therein, a closure cap end or guide pro viding a bore, a diaphragm or shield interposed between the expansion material and the cap, and a power member or piston guided for movement within the bore and bottoming on the diaphragm. When the temperature of the expansion material is raised to a predetermined point, the material expands and the expansion is transmitted through the diaphragm to the power member which is thereby caused to move axially within the bore.

The presently known power members have several distinct disadvantages which diminish the operable life thereof. This is especially so in thermal elements utilizing small diameter and long stroke power members. ()ne of the problems as evidenced in the reverse poppet type valve, is that the initial opening load resulting from a large pressure drop across the poppet has caused severe strain on the assembly. In the case of reverse poppet waterline thermostats, the strain has caused the stirrup means to buckle as well as placing undue strain and stress on the small diameter power member. This strain causes the power member to prematurely breakdown and prevent the proper operation of the waterline thermostat. A small diameter power member being designed to take approximately a 12 to 15 pound load may be under a 50 to 90 pound load during the first 0.050 to 0.060 inch of opening. Fluttering the instability of the start-to-open point is a result which causes excessive wear and stress on the valve member and especially the power member and the stirrup means in a reverse poppet waterline thermostat.

The smaller the piston diameter the more travel that can be obtained from a given amount of expansion material. This allows the possibility of reducing the amount of material as well as the size of the metal and rubber parts utilized to make up the responsive elements. However, small diameter piston elements have not been able to utilize their beneficial properties, in that, slight changes in temperatures and pressures cause a more pronounced reaction therewith than would be caused by a larger diameter piston element and also the undue strain thereon subjects them to premature rupture.

Therefore, it is an object of the present invention to provide a thermal responsive element utilizing the beneficial aspects of small diameter power members without subjecting the thermal responsive elements to the detriments of prior power members.

It is another object of the present invention to provide a thermostatic power element which incorporates the beneficial aspects of a large diameter power member with the beneficial aspect of a small diameter power member to provide an improved thermal responsive element.

It is still another object of the present invention to provide a thermal responsive power element wherein the initial movement exerts a considerably greater force per pound per square inch internal pressure than subsequent movement of said power member.

3,407,663 Patented Oct. 29, 1968 It is another object of the present invention to provide a thermostat in which the initial motion of the power member is reduced even though a high expansion ma terial and a small diameter power member is utilized.

It is another object of the present invention to provide a thermostat in which a large diameter piston is operated to actuate the power element during the beginning of the opening stroke of the power member and the remainder of the stroke is accomplished by a small diameter piston.

It is another object of the present invention to provide a thermostat having a power element with a small di ameter power member piston extending into the casing containing expansion material and being contacted by a diaphragm and having coaxially slidably connected thereto a second larger diameter piston which is operatively connected to the power member to move said power member during the expansion of said expansion material and restrained by a thermostat guide means to allow only limited movement of said large diameter piston wherein upon initial expansion of the expansible material the large diameter piston and the small diameter piston portion move the power member to take and absorb the brunt of the opening pressures for a short predetermined distance of the opening stroke while the remaining portion of the opening stroke is accomplished by the smaller diameter piston alone.

These and other objects, features and advantages of the present invention will become more apparent from a careful consideration of the following detailed description, when considered in conjunction with the accompanying drawings illustrating preferred embodiments of the present invention, and wherein like reference numerals and characters refer to like and corresponding parts throughout the several views.

On the drawings:

FIGURE 1 is a longitudinal cross-sectional view of a thermal responsive element of the present invention;

FIGURE 2 is -a longitudinal cross-sectional view of the thermal responsive element illustrated in FIGURE 1 illustrating a sequence in the operation of the thermal responsive element;

FIGURE 3 is a longitudinal cross-sectional view of another embodiment of the power element of the present invention;

FIGURE 4 is a partial longitudinal cross-sectional view with parts in elevation of another embodiment of the thermal responsive element of the present invention;

FIGURE 5 is a longitudinal cross-sectional view of still another embodiment of the thermal responsive element of the present invention;

FIGURE 6 is a partial cross-sectional view of the thermal responsive element illustrated in FIGURE 5 illustrating an operational phase of said thermal responsive element; and

FIGURE 7 is a longitudinal cross-sectional view of another embodiment of a thermal responsive element manufactured in accordance to the principles of the present invention.

As shown on the drawings:

The thermal responsive element of the present invention has a casing containing suitable heat expansible material, a guide connected to the top portion of the casing and extending upwardly therefrom defining a counterbored power member passage therethrough. A power member having a first small diameter piston portion to receive the forces exerted by the expansible material and an enlarged piston portion. A flexible boot or diaphragm is connected to the power member and is sealin-gly attached to the casing. A large diameter piston is slidably mounted within the guide counterbore and has one end abutting the power member shoulder between the large and small diameter portions thereof. The large diameter piston is connected to' the diaphragm so that when the expansible material is expanded, pressure is first exerted against a large piston area for a predetermined distance and then will be exerted only against the small diameter portion of the power member. In this manner, by having an initially larger diameter piston, the amount the piston can be moved due to compressibility of the expansion material and the rubber parts is substantially reduced by the initial large diameter piston.

In this manner better control is obtained due to the fact that cycling is reduced because of the smaller motion per degree change temperature at the beginning of the opening while the total opening necessary is still accomplished Without increasing the size of the thermostat, by using a smaller piston to complete the opening.

Referring to FIGURES 1 and 2 there is illustrated a thermal responsive element 11 of the present invention. The thermal responsive element 11 has a cup-shape casing 12 with flanges 13 extending outwardly from its open end. The casing 12 contains atemperature sensitive substance such as a microcrystalline wax which fuses and expands when raised above a given critical temperature and which can be compressed to a smaller volume upon cooling to a point below that critical temperature. The exact nature of the material 14 is determined in accordance with the desired operating characteristics of the power element.

A cylindrical guide 16 has a first passage 17 passing therethrough and a counterbored second passage 18 concentric therewith. The counterbored passage 18 forms a shoulder 19 at one end with the first passage and has diverging walls 21 at the other end. The diverging walls 21 curve to meet the inner face of a radially outwardly extending flange end wall 22. The innerface of the flange end wall is stepped to form a peripheral raised portion 23 and "an inner reduced portion 24 that meet with the Surface of the diverging walls 21. The outer diameter of the guide flange 22 and the outer diameter of the casing flange 13 are appropriately identical.

A flexible rubber boot 26 defining a cylindrical bore 27 has a conical bottom wall 28 substantially in the center thereof. Said boot has a radially outwardly extending flange 29 extending outwardly therefrom with a lower portion 30 having a converging outer surface 31 extending from one end of said flange 29 and a rounded end surface 32 and an upper portion 35 having a converging outer surface 33 extending from the other end of said flange 29 and said end surface converging to the cylindrical outer wall 24 which forms the annular end wall 36. The flexible deformable rubber boot 26 is mounted on the casing 12 by seating the bottom face 29a of the flange 29 on the face of the casing flange 13 with the lower portion 30 being centrally within the casing 12 so that it is surrounded by the expansible material 14. The guide 16 with its flange 22 is placed in position so that the innerface of the flange 22 contacts the boot flange 29. Thus, the boot flange 29 has a slightly larger thickness than the height of the annular raised portion 23 to thereby effec tively seal and retain the expansible material within the casing 12 and prevents any deleterious materials from entering the casing 12.

The guide is attached to the casing by suitable annular retainer ring means 37 that is clamped over the outer faces of the guide flange 22 and the casing flange 13 to retain the guide and casing members in fixed positions relative to one another.

A cylindrical large diameter piston 38 is slidably mounted within the guide counterbore 18. The piston 38 has an outer diameter approximately equal to the diameter of the counterbore but is mounted so that it is slidable therein. The piston also has an inner diameter less than the diameter of the first guide passage 17.

The cylindrical piston 38 has an end wall 39 that abuts the end wall 36 of the rubber boot 26. The length of the cylindrical piston 33 is a predetermined amount smailer 4 than the length of the counterbore 18 so that cylindrical piston may be slidably actuated in said counterbore.

A power member 41 having an enlarged diameter portion 42 and a small diameter portion 43 concentrically extending from one end thereof to form a shoulder 44 there'between. The large diameter portion has an outer diameter substantially equal to the diameter of the first guide passage 17 but is mounted to be slidable therein and the small diameter portion 43 hereinafter referred to as the power member piston. The power member piston,

diameter is slightly greater than the diameter of the boot chamber 27 to allow the small diameter piston to be positively seated within the rubber boot chamber and to be grasped by the sides of said boot chamber. The dimensions of the power member piston portion are predetermined so that when the small diameter piston portion completely fills the boot chamber 27, the cylindrical piston 38 will surround the power member piston with one end thereof abutting the boot end 36 and the other end thereof abutting the power member shoulder 44. The inner diameter of the cylindrical piston 33 is approximately equal to the outer diameter of the power member piston 43 with the piston 43 being slidably mounted therein. When the thermal expansible material is in its cold nonexpansible condition, the thermal responsive element, as illustrated in FIGURE 1, one end of the cylindrical piston 38 abuts the end wall 36 and the power member shoulder 44 with the other end of the cylindrical piston being spaced a predetermined amount from the guide counterbore shoulder 19.

In operation, the thermal responsive element 11 may be for instance, placed in position in a suitable control valve member wherein the casing 12 is in contact with fiuid to sense the temperature of the fluid, i.e., a waterline thermostat wherein the casing 12 is upstream of the valve member.

When the fluid reaches the critical temperature of the expansible material 14 within the casing, the material expands and exerts an upward force on the flexible deformable boot 26. The boot 26 transfers this force to the power member piston 43 and the cylindrical piston 38 wherein the piston power member 42 is moved up wards only a small amount and a portion of the pressure exerted by the fluid expansible material is translated to the cylindrical piston 38. Therefore, in a waterline ther mostat which is designed to take approximately a 12 to 15 pound load and wherein the valve may be under a 50 to pound load during the first 0.050 to 0.060 inch of opening the power member utilizes a large crosssectional area consisting of the cross-sectional area of the cylindrical piston 38 and the power member piston 43 to overcome the initial high loads exerted on the reverse poppet valve of a waterline thermostat and thereby substantially reduce the strain placed on the small diameter power member piston. In this manner, it is possible to provide a small diameter power member piston that only moves in an initial relatively small distance and to prevent excessive wear and stress on the valve member as well as the small diameter of the power piston. As the expansible material 14 expands, it exerts an upward force on the power member 41. The top of the power member 42 in a reverse poppet waterline thermostat is fixed against a stirrup means so that it may not move axially. Therefore, as the material expands the guide member 16 and casing 12 are urged downwardly. The distance between the counterbore shoulder 19 and the adjacent end of the cylindrical piston 38 is that distance which is required to withstand the initial opening loads, i.e., 0.050 to 0.060 inch in a waterline thermostat designed to take approximately a 12 to 15 pound load with the power member piston having approximately 0.125 inch diameter and the cylindrical piston having approximately 0.219 inch outer diameter.

After the end of the cylindrical piston abuts against the guide counterbore shoulder 19, as is illustrated in FIGURE 2, the expanding material 14 then exerts all of its pressure against the small piston 43 to rapidly open the valve member. This second exertion of the expanding material against only the small diameter power member piston utilizes the high stroke ability of the small diameter piston without subjecting the small diameter piston to the initial critic-a1 opening temperatures and pressures. The double action thermostatic power element of the present invention is practical and advantageous in many ways. The large and small pistons are tailored to the requirements of a given application; the large piston diameter 'being adjusted to take the brunt of opening pressures while the smaller piston is designed to give the required stroke under the reduced pressure of normal flow. Increased uniformity of the setting point is achieved by spreading the initial expansion pressure over a greater area making the motion less liable to force changes. Also, in the case of waterline thermostats, the thermostatic member increases the life of said thermostats while decreasingthe amount of materials needed to manufacture said thermostats.

Referring to FIGURE 3 there is illustrated another embodiment of a thermostatic power element 51 manufactured in accordance to the principles of the present invention. The thermostat 51 has a similar construction as the thermostat 11 with similar casing means 12, expansion material 14, guide means 16, and boot means 26. The thermostat 51 however contains an antichafe ring 52 positioned between the end 36 of the boot 26 and a cylindrical piston 53. The cylindrical piston has an enlarged base 54 with a cross-sectional area equal to the crosssectional area of the antiehafe ring 52 and has its end face 53a abutting against the top face 52a of said antichafe ring 52. The enlarged base portion 54 has an outer diameter substantially equal to the diameter of the counterbore' 18 and is slidably mounted therein. The cylindrical piston 53 is positioned within the thermostat 51 with the outer diameter of the piston being substantially equal to the outer diameter of the guide passage 17 and being slida'bly mounted therein. The piston extends from the top of the guide 19 through the guide passage 17 into abutment with the antichafe ring 52. The enlarged base flange portion 54 has its outer shoulder face 56 spaced a predetermined distance from the guide counterbore shoulder 19. The top of the cylindrical piston has aifixed thereto a cylindrical guide ring 57 with the guide 19 moving relative to the guide ring 57.

The guide ring 57, the cylindrical piston 53, the antichafe ring 52, and the boot chamber 27 are all concentric to one another defining a concentric power member passageway. A cylindrical power member 58 having a uniform outer diameter equivalent to the diameter of the power member piston portion 43 acts as the power member piston is inserted in said concentric power member passageway.

A similar thermostat to that illustrated in FIGURE 3, would be possible by making the guide ring 57 an integral part of the cylindrical power member 58.

The thermostat 51 operates in a similar manner to the thermostat 11 with the expansion of the material 14 exerting pressure on a cross-sectional area equal to the crosssectional area of the large piston base 54 and the conical end area of the small diameter piston of the power member. The cylindrical piston moves upwards a predetermined amount in the guide counterbore 18 until its upper base face 56 abuts the guide counterbore shoulder 19. Then the remainder of the upward stroke of the power member piston 53 is accomplished by the expansible material and rubber boot exerting pressure only on said power member piston.

Referring to FIGURE 4 there is illustrated another thermostat 61 embodying the principles of the present invention wherein a thermostat is formed of a single cup 62 instead of a casing and guide member. The cup 62 forms a cylindrical chamber 63 with an open end 64.

The inner walls forming the cylindrical chamber 63 are provided near the end, with a pair of spaced inwardly extending annular protrusions 66 and 67. The protrusion 66 is a frusto-conical protrusion and the protrusion 67 is a semicircular nipple protrusion. Between the protrusions 66 and 67 is located a cylindrical or disk-like piston 68 having an outer diameter equal to the diameter of the chamber 63 and being slidably mounted therein. The thickness of the cylindrical piston 68 and the distance between the protrusions 66 and 67 are predetermined so that the piston may move a predetermined amount between said protrusions.

The rubber boot 69 having a cylindrical chamber 71 therein is mounted within the cup 62 over expansible material 14in the lower portion of the cup 62. The rubber boot is afiixed to the cup 62 by the frusto-conical annular protrusion which effectively seals the expansible material within the lower portion of the cup 62. The top portion of the boot 69 abuts against the cylindrical piston 68.

A power member 72 having a lower small diameter power member piston portion 73 and a top portion 74 extends outwardly from the open end of the cup 62. The power member piston is inserted within the rubber boot chamber 71 and through the piston 68. The power member piston has a top'shoulder portion 75 against which a top surface 76 cylindrical piston abuts, said cylindrical cylinder having a diameter larger than the diameter of said shoulder 75.

In operation, when the expansible material 14 expands, the pressure exerted thereby is first exerted across the cross-sectional area of the cylindrical piston 68 and the end area of the power member piston 73 with the power member moving upwardly until the top surface 76 of the cylindrical piston 68 abuts against the protrusion 67. Then the second action portion of the double action thermostat 61 occurs, the pressure of the expanding material is only exerted on the power member piston 73 The power member piston is brought back into its original position when the temperature is lowered by contraction of the expansible material 14 and spring means (not shown) urging said power member piston in a downward direction.

Referring to FIGURES 5 and 6 there is illustrated another thermostat 81 manufactured in accordance to the embodiments of the present invention. The thermostat 81 utilizes instead of a flexible boot having a small diameter piston engaging chamber a rubber plug 82 having a cylindrical top end 83 with its face 84 abutting against an end face 86 of a small diameter power member piston portion 87 of a power member 88. The cylindrical plug has conical side 89 diverging from the cylindrical top portion 83 and a bottom cylindrical portion 91 extending from said conical walls 89. Connected to the bottom portion of the cylindrical walls 91 is a rubber diaphragm 92 having an annular end protrusion 93. The end protrusion is sealingly fastened to an enlarged base 94 of a guide member 96 by a corresponding annular groove 97 formed in said base end wall.

The guide member 96 defines a power member first passage 98 and a counterbored second passage 99 concentric therewith forming a guide shoulder 101 therebetween. A cylindrical piston 102 having a circular end wall 103 facing the shoulder 101 and a conical end wall 104 engaging the rubber plug conical wall 89. The cylinder piston end wall 103 abuts against a shoulder 106 formed between the enlarged portion and the small diameter power member piston p0rtion 87 of the power member 88. A casing 107 containing expansible material 14 is affixed to the guide 96, and the rubber diaphragm 92 sealingly isolates the expansible material from the rubber plug 82 and the guide 96. When the expansible material is in its unexpanded state, the distance between the piston end wall 103 and the guide shoulder 101 is predetermined so as to be equal to the desired initial opening distance.

In operation, the thermostat 81 is initially in the position as illustrated in FIGURE 6. When the material 14 expands, pressure is exerted againstthe diaphragm 92 and thereby against a first large cross-sectional area which comprises the cross-sectional area of the cylindrical piston and cross-sectional area of the power member piston 87. This pressure is exerted against this first large cross-sectional area until the cylinder piston end wall 103 abuts against the guied shoulder 101, as is illustrated in FIG- URE 5. Then the pressure exerted by the expanding material 14, is exerted against the second small cross-sectional areaof the small diameter power member piston 87 to form the double action thermostat 81.

Another embodiment of the present invention is illustrated by FIGURE 7 wherein there is shown athermostat 111 similar to the thermostat 81 except that the thermostat 111 utilizes a plug 112 having a cylindrical sleeve portion 113. defining a power member piston chamber 114 for engaging the small diameter power member piston 87. The cylindrical sleeve 113 has a circular end wall 116 that abuts against the bottom surface of a cylindrical or disklike piston 177. The disk-like piston hasits top wall 118 abutting against the shoulder 106 of the power member 88 and adapted to abut against the shoulder 101 of the guide member 96 when the expansible material 14 has expanded. The thermostat illustrated in FIGURE 7 is in the position wherein the expansible material 14 has expanded to urge an initial force against a first large cross-sectional area which comprises the cross-sectional area of the cylindrical piston 117 and the cross-sectional area of the small diameter power member piston 87 wherein the cylindrical piston end wall 103 is placed in abutment with the guide shoulder 101. The second action phase of the thermostat will then occur wherein the pressure of the expanding material will be exerted only across the cross-sectional area of the small diameter power member piston portion 87.

I have therefore devised a temperature sensitive power unit having a variable power output and stroke wherein, specifically, the power member initially moves through a short stroke with great power and thereafter moves with relatively less power through a considerably greater stroke. Such a power unit has particular utility in use with fluid control valves employing a poppet valve member which must be opened as a function of temperature variances, ambient the temperature sensitive portion of the unit against the force of pressurized liquid and so has been described in this environment, although it is realized that such unitshave almost unlimited application in those instances in which a thermostatically actuable power source is required.

The dimensional characteristics of the thermostats of the present invention may be varied in accordance to the functions they are to perform.

It will be understood that these embodiments of the invention have been used for illustrative purposes only and that various modifications and variations in the present invention may be effected without departing from the spirit and scope of the novel concepts thereof.

I claim:

1. A double-action thermostat having a housing containing a thermal expansible material operatively connected to a power member wherein expansion of said expansible material exerts a pressure to move the casing and power member relative to each other, comprising:

a first piston, I

a power member piston affixed to said power member,

a resilient deformable rubber diaphragm mounted to said housing sealingly separating the power member piston and first piston from the expansible material,

one face of said diaphragm contacting the expansible material,

a deformable rubber plug having one side thereof contacting the outer face of said diaphragm and the other side contacting said first piston and said power member piston,

said first piston being slidably mounted in said housing for limited movement therein,

- said power member being slidably mounted in said housing to'provide relative movement between said housing and the power member,

whereby initial expansion of said expansible material exerts pressure on the first and power member pistons to relatively move the casing and power member a predetermined distance until the first power member moves its limited distance in the housing and then the expansible material pressure is used on only the power member piston to move the power member and the housing relative to each other.

2. A double-action thermostat comprising:

a cup-shaped casing having an open end wall,

a predetermined amount of thermal pressure producing expansible material within said casing,

a deformable rubber boot having:

an outwardly extending flange dividing said boot into an upper portion and a lower portion, and

said .upper portion having outerwallsconverging from a top face of the boot flange toward vertically extending walls that terminate, in a top flat boot end wall,

,said lower portion having walls converging from a bottom face of the boot flange to a bottom convex boot end wall,

a power member piston chamber formed by said boot having its open end formed by the top end wall and its bottom spaced inwardly from the bottom end wall,

a guide member having a first guide passage, a second counterbored guide passage defining a guide shoulder between said first and second guide passages, and a diverging end passage having walls diverging from the end of the counterbored guide passage,

a guide end wall having its end surface extending outwardly from one end of the diverging guide passage wall with an annular protrusion on the periphery thereof,

means to affix said guide member to said casing with said boot flange sandwiched between said guide end wall and said casing end wall with said boot lower portion extending into said casing and said expansible material being sealed within said casing from said bootupper portion, I

a power member having a power member piston portion,

said power member piston portion having dimensions slightly larger than the dimensions of said boot chamber,

said power member piston normally being within and filling said boot chamber,

a first tubular piston slidably and concentrically mounted around said power member piston and having one end contacting and facing the boot top end wall and the other end normally spaced a predetermined distance from the guide shoulder,

said first piston being slidable within guide counterbore passage, and r I said guide shoulder limiting the movement of said first piston wherein when the other endof the first piston abuts the guide shoulder the power member piston and the first piston move relative to each other,

whereby upon expansion of the expansible material initial pressure is exerted across the first piston area and the power member piston area to relatively move the first and power member pistons and the guide memberuntil the first piston abuts the guide shoulder and then pressure is exerted on only the power member piston area to provide high stroke actuation for the power member.

3. A double-action thermostat comprising:

a cup-shaped casing having a flanged flat faced open end wall;

a predetermined amount of thermal pressure producing expansible material within said casing,

a deformable rubber booth having:

an outwardly extending flange dividing said boot into an upper portion and a lower portion, and

said upper portion having outer walls converging from a top face of the boot flange to upwardly extending 'walls that define a top flat boot end wall,

said lower portion having walls converging from a bottom face of the boot flange to a bottom convex boot end wall,

a power member piston chamber formed by said boot having its open end formed by the top end wall and its bottom spaced inwardly from the bottom end wall,

a guide member having a first guide passage, a second counterbored guide passage defining a guide shoulder between said first and second guide passages, and a diverging end passage having walls diverging from the end of the counterbored guide passage,

a flanged guide end wall extending outwardly from the base of said guide member and having its end surface extending outwardly from one end of the diverging guide passage walls with an annular periphery protrusion,

the thickness of said boot flange being greater than the height of said annular guide end wall protrusion,

means to aflix said guide member to said casing with said boot flange sandwiched between said guide flange end wall and said casing flange end wall with said boot lower portion extending into said casing and said expansible material being sealed from said boot upper portion and within said casing,

a power member having a power member piston portion,

said power member piston portion having a conical end wall and dimensions slightly larger than the dimensions of said boot chamber,

said power member piston normally being within said boot chamber,

an antichafe ring in sliding contact with said power member piston and slidably mounted in said guide counterbore with one end thereof in contact with the boot top end wall,

a first piston in sliding contact with said power member piston and having one end abutting the antichafe ring and the other end normally spaced a predetermined distance from the guide shoulder, and

said guide shoulder limiting the movement of said first piston wherein when the other end of the first piston abuts the guide shoulder the power member piston and the first piston move relative to each other,

whereby upon expansion of the expansible material initial pressure is exerted across the first piston area and the power member piston area to relatively move them and the guide member until the first piston abuts the guide shoulder and then pressure is exerted on only the power member piston area to provide high stroke actuation to the power member.

4. A double-action thermostat comprising:

a cup-shaped housing forming a chamber, with an open end, t

a predetermined amount of thermal pressure producing expansible material within said housing,

a pair of axially spaced protrusions extending inwardly from the walls of housing chamber and above the expansible material,

a deformable rubber boot having:

a power member piston chamber formed by said boot having its open end facing the housing chamber open end, and

means to attach the boot to one protrusion furthest from the housing chamber open end to effectively seal the expansible material in the housing,

a power member having a power member piston portion, said power member piston portion having a conical end wall and dimensions slightly larger than the dimensions of said boot chamber,

said power member piston normally being within said boot chamber,

a first piston in sliding contact with said power member piston and having one end abutting a boot end wall and the other end normally spaced a predetermined distance from the other chamber wall protrusion,

said first piston being slidable within the housing between said pair of chamber wall protrusions,

said other chamber protrusion limiting the movement of said first piston wherein when the other end of the first piston abuts the other chamber protrusion the power member piston and the first piston move relative to each other,

whereby upon expansion of the expansible material initial pressure is exerted across the first piston area and the power member piston area to move together the first and power member pistons to the guide member until the first piston abuts the other chamber protrusions and then pressure is exerted on only the power member piston area to provide high stroke actuation to the power member.

5. A double-action thermostat comprising:

a cup-shaped casing having a flanged flat faced open end wall,

a predetermined amount of thermal pressure producing expansible material within said casing,

a deformable rubber boot having:

a flexible deformable rubber diaphragm extending across said casing open end wall and secured to the casing to seal the expansible material within said casing,

said diaphragm having one wall thereof in contact with the expansible material and the other opposite wall having a central conical surface,

a resilient deformable plug having one end wall with a central concave surface having approximately the same dimensions as the diaphragm conical surface,

said plug contacting the diaphragm with the concave plug surface in contact with the diaphragm conical surface,

the other end wall of the plug being a stepped end wall with a frusto-conical surface and a flat surface,

a guide member having a first guide passage, and a second counterbored guide passage defining a guide shoulder between said first and second guide passages,

a flanged guide end wall extending outwardly from the base of said guide member and having its end surface extending outwardly from the end of the counterbored guide passage and having: an annular protrusion on the periphery thereof,

means to affix said guide member to said casing with said diaphragm sandwiched between said guide flange end wall and said casing flange end wall with said expansible material being sealed within saidvcasing and from said plug,

a power member having a power member piston portion,

said power member piston portion having a fiat end wall in contact with the plug flat end surface,

a first piston in slidable contact with said power member piston and having a frusto-conical end abutting the plug frusto-conical end surface and the other end normally spaced a predetermined distance from the guide shoulder,

said first piston being slidable within the guide counterbore passage, and

said guide shoulder limiting the movement of said first piston wherein when the other end of the first piston l 1 abuts the guide shoulder the power member piston and thefirst piston move relative to each other,

whereby upon expansion of expansible material initial pressure is exerted across the first piston area and the power member piston area to relatively move the guide member and the first and power member pistons until the first piston abuts the guide shoulder and then pressure is exerted on only the power member piston area to provide high stroke actuation for the power member.

'6. A double-action thermostat comprising:

a cup-shaped casing having a flanged fiat faced open end wall,

a predetermined amount of thermal pressure producing expansible material within said casing,

a flexible deformable rubber diaphragm extending across said casing open end wall and secured to the casing to seal the expansible material within said casing,

said diaphragm having one wall thereof in contact with the expansible material and the other opposite wall having a central conical surface,

a resilient deformable plug having one end wall with a central concave surface having approximately the same dimensions as the diaphragm conical surface,

said plug contacting the diaphragm with the concave plug surface in contact with the diaphragm conical surface,

the other plug end wall defining the mouth of a power member piston chamber formed within said plug,

a guide member having a first guide passage, and a second counterbored guide passage defining a guide shoulder between said first and second guide passages,

a flanged guide end wall extending outwardly from the base of said guide member and having its end surface extending outwardly from the end of the counterbored guide passage and having an annular protrusion on the periphery thereof,

means to affix said guide member to said casing with said diaphragm sandwiched between said guide flange end wall and said casing flange end wall with said expansible material being sealed within said casing and from said plug,

a power member having a power member piston portion, said power member piston portion having dimensions slightly larger than the dimensions of said plug chamber,

said power member piston normally being within said plug chamber,

a first piston in slidable contact with said power member piston and having one end abutting the plug other end wall and the other end normally spaced a predetermined distance from the guide shoulder,

said first piston being slidable within guide counterbore passage, and

said guide shoulder limiting the movement of said first piston wherein when the other end of the first piston abuts the guide shoulder the power member piston and the first piston move relative to each other,

whereby upon expansion of the expansible material initial pressure is exerted across the first piston area and the power member piston area to relatively move the first and power member pistons and the guide member until the first piston abuts the guide shoulder and then pressure is exerted on only the power member piston area to provide high stroke actuation for the power member.

7. A double-action thermostat comprising: a cup-shaped casing, a predetermined amount of thermal pressure producing expansible material within said casing, a deformable rubber boot having:

an outwardly extending flange dividing said boot into an upper portion and a lower portion, and said upper portion having outer walls converging from a top face of the boot flange toward ver- 12 tically extending walls that terminate in a top flat boot end wall, said lower portion having walls convering from a bottom face of the boot flange to a bottom convex boot end wall,

a power member piston chamber formed by said boot having its opening end formed by the top end wall and its bottom spaced inwardly from the bottom end wall,

a guide member having a first guide passage and an axially formed radially enlarged secondguide passage,

a guide shoulder formed between said lfirst and second guide passages, said guide member afiixed to said cup-shaped casing for having said upper portion of said boot extend within said second guide passage,

a piston sleeve slidably positioned within said second guide passage between said upper portion of said boot and said guide shoulder, and

a power piston disposed within said piston chamber of said boot and extending through said piston sleeve for being received within said first guide passage.

8. A double-action thermostat comprising:

a cup-shaped casing,

a predetermined amount of thermal pressure-producing expansible material within said casing,

a deformable rubber boot having:

a flexible deformable rubber diaphragm extending across said casing open end wall and secured to the casing to seal the expansible material within said casing,

said diaphragm having one wall thereof in contact with the expansible material and the other opposite wall having a central conical surface,

a resilient deformable plug having one end wall with a central concave surface having approximately the same dimensions as the diaphragm conical surface,

said plug contacting the diaphragm with the concave plug surface in contact with the diaphragm conical surface,

the other end wall of the plug being a stepped end wall with a frusto-conical surface and a flat surface,

a guide member having a first guide passage and an axially formed radially enlarged second guide passage,

a guide shoulder formed between said first and second guide passages,

said guide member affixed to said cup-shaped casing for having said upper portion of said boot extend within said second guide passage,

a power member having a flat end wall in contact with the plug flat end surface,

a piston sleeve in slidable contact with said power member within said second guide passage and having a frusto-conical end abutting the plug frustoconcial end surface and the other end normally spaced a predetermined distance from the guide shoulder.

9. A double-action thermostat comprising:

a cup-shaped casing,

a predetermined amount of thermal pressure-producing expansible material within said casing,

a deformable rubber boot having:

an outwardly extending flange dividing saidboot into an upper portion and a lower portion, and

said upper portion having outer walls converging from a top face of the boot flange toward vertically extending walls that terminate in a top flat boot end wall, said lower portion having walls converging from a bottom face of the boot flange to a bottom convex boot end wall,

a power member piston chamber formed by said boot having its open end formed by the top end wall and its bottom spaced inwardly from the bottom end wall,

a guide member having a first guide passage and an axially formed radially enlarged second guide passage,

a guide shoulder formed between said first and second guide passage, said guide member aflixed to said cupshaped casing for having said upper portion of said boot extend within said second guide passage, said second guide passage having a frusto-conical profile conforming to said upper portion of said boot,

a piston sleeve slidably positioned within said second guide passage between said upper portion of said boot and said guide shoulder, and

a power piston disposed within said piston chamber of said boot and compressing the upper portion of said boot against the conforming frusto-conical profile of said second guide passage,

References Cited UNITED STATES PATENTS 2,433,221 12/1947 Huber 92101 X 2,781,784 2/1957 Baker 73368.4 X 2,873,609 2/ 1959 Von Wangenheim 73368.3 X 2,986,936 6/1961 Vernet 73-368.3 3,016,747 1/ 1962 Vernet 73-3683 3,131,269 4/1964 Asakowa 73-363 X 3,183,720 5/1965 Baker 73368.3

15 S. CLEMENT SWISHER, Acting Primary Examiner.

WILLIAM HENRY, Assistant Examiner. 

1. A DOUBLE-ACTION THERMOSTAT HAVING A HOUSING CONTAINING A THERMAL EXPANSIBLE MATERIAL OPERATIVELY CONNECTED TO A POWER MEMBER WHEREIN EXPANSION OF SAID EXPANSIBLE MATERIAL EXERTS A PRESSURE TO MOVE THE CASING AND POWER MEMBER RELATIVE TO EACH OTHER, COMPRISING: A FIRST PISTON, A POWER MEMBER PISTON AFFIXED TO SAID POWER MEMBER, A RESILIENT DEFORMABLE RUBBER DIAPHRAGM MOUNTED TO SAID HOUSING SEALINGLY SEPARATING THE POWER MEMBER PISTON AND FIRST PISTON FROM THE EXPANSIBLE MATERIAL, ONE FACE OF SAID DIAPHRAGM CONTACTING THE EXPANSIBLE MATERIAL, A DEFORMABLE RUBBER PLUG HAVING ONE SIDE THEREOF CONTACTING THE OUTER FACE OF SAID DIAPRAGM AND THE OTHER SIDE CONTACTING SAID FIRST PISTON AND SAID POWER MEMBER PISTON, 